The present application relates to battery packs comprising a battery cell contained in a case.
Battery packs including a battery case containing therein a primary battery or a secondary battery and a wiring circuit board have been conventionally used. If the electrolyte leaks out from a battery cell in such battery packs, wrong connection may occur by corrosion of the wire of the wiring circuit board or reversely, a short circuit may occur. Thus, it was proposed to place a liquid-absorbing element capable of absorbing electrolytes at a position in contact with or in proximity to the battery in the battery packs in order to avoid the problem of corrosion or short-circuit even if the electrolyte leaks out (e.g., see Japanese Patent Application No. 2001-351588). Such liquid-absorbing elements include nonwoven fabrics, liquid-absorbing resins, porous plastics, nonwoven fabrics or porous plastics held with a liquid-absorbing resin, and the like, and these are placed to fill gaps between battery cells in the battery case or bonded to the wiring circuit board excluding the circuit zone or the wall surface of the battery case by using an adhesive or the adhesiveness of the liquid-absorbing elements per se.
However, if such a liquid-absorbing element is placed to fill gaps between battery cells, the liquid-absorbing element must also be removed and inserted again when the battery cells are replaced. If the liquid-absorbing element is bonded to the wall surface of the battery case or the substrate with an adhesive or the adhesiveness of the liquid-absorbing element per se, the swelling force acts as a peel force on the bonded surface of the liquid-absorbing element to the wall surface of the case or the board when the liquid-absorbing element has been swollen by absorbing the electrolyte. As a result, the liquid-absorbing element might be displaced from the wall surface of the battery case or an intended location on the board and move to an undesirable position such as the circuit zone.
A previous approach to this problem was to block the displacement of the liquid-absorbing element by a partition or the like, but caused a design constraint.